UNIVERSITY  OF  CALIFORNIA   PUBLICATIONS 

IN 

AGRICULTURAL    SCIENCES 

Vol.  3,  No.  6,  pp.  103-130  March  9,  1918 


CHANGES  IN  THE  CHEMICAL  COMPOSITION 
OF  GRAPES  DURING  RIPENING 

BY 

F.  T.  BIOLETTI,  W.  V.  CRUESS,  and  H.  DAVI 


The  investigations  reported  in  this  paper  were  undertaken  to 
determine  the  changes  in  chemical  composition  of  vinifera  varieties 
of  grapes  in  California  during  the  growing  and  ripening  stages.  A 
survey  of  the  literature  indicated  that,  although  the  subject  had  been 
quite  fully  investigated  in  Europe  with  vinifera  varieties  and  in 
America  with  the  native  varieties,  very  little  had  been  published  upon 
the  ripening  of  vinifera  varieties  under  California  Conditions.  A 
great  many  analyses  of  different  varieties  of  grapes  have  been  made 
by  chemists  of  the  University  of  California  Experiment  Station,  nota- 
bly by  G.  E.  Colby,  and  are  reported  in  the  publications  of  this  station.1 
A  paper  by  G.  E.  Colby2  gives  data  upon  the  nitrogen  content  of  a 
number  of  varieties  of  ripe  vinifera  grapes.  Most  of  the  analyses, 
however,  do  not  show  the  changes  in  composition  during  ripening. 

Of  the  more  recent  European  investigations3  some  deal  with  the 
changes  in  general  composition,  others  are  confined  to  a  discussion  of  a 
single  component,  such  as  sugar,  or  coloring  matter,  or  acid  principles. 

The  changes  in  composition  of  American  varieties  of  grapes  during 
ripening  have  been  studied  quite  thoroughly  by  W.  B.  Alwood4  and 
his  associates.     These  investigations  gave  particular  attention  to  the 


1  Hilgard,  E.  W.,  The  composition  and  classification  of  grapes,  musts,  and 
wines.  Rept.  of  Viticultural  Work,  Univ.  Calif.  Exper.  Sta.  Rep.,  1887-93,  pp. 
3-360. 

2  Colby,  G.  E.,  On  the  quantities  of  nitrogenous  matters  contained  in  Cali- 
fornia musts  and  wines.     Ibid.,  pp.  422-446. 

3  Kelhof er,  W.,  The  grape  in  the  various  stages  of  mature tj;  trans,  by  E. 
Zardetti.     Gior.  Vin.  Ital.,  vol.  34  (1908),  no.  30,  pp.  475-477. 

Barberon,   G.,   and   Changeant,   F.,   Investigations   on   the    development    and 


104  University  of  California  Publications  in  Agricultural  Sciences         [Vol.  3 

increase  in  sugar  content  and  changes  in  acidity  during  the  period 
in  which  the  grapes  were  under  observation.  Alwood  and  other  mem- 
bers of  the  Bureau  of  Chemistry,  United  States  Department  of  Agri- 
culture, have  also  published  a  number  of  reports4  on  the  general 
composition  of  American  varieties  of  grapes  as  affected  by  season, 
locality,  etc. 

The  most  notable  changes  taking  place  during  ripening  were  found 
by  the  European  and  American  investigators  mentioned  above  to  be : 
( 1 )  increase  in  total  sugar ;  ( 2 )  decrease  in  ratio  of  glucose  to  fructose  ; 
(3)  decrease  in  total  acid;  (4)  increase  in  ratio  of  cream  of  tartar  to 
total  acid  due  to  decrease  in  total  acid ;  (5)  decrease  in  tannin  ;  and  (6) 
increase  in  coloring  matter.  The  cream  of  tartar  and  protein  change 
very  little  in  percentage  during  ripening,  although,  according  to  the 


composition  of  varieties  of  grapes  in  Abraon-Durso.  Ann.  Soc.  Agr  Sci.  et  Ind., 
Lyon  (8),  vol.  1  (1903),  pp.  97-159. 

Laborde,  J.,  The  transformation  of  the  coloring  matter  of  grapes  during 
ripening.     C.  E.  Acad.  Sci.  (1908),  vol.  17,  pp.  753-755. 

Martinand,  V.,  On  the  occurrence  of  sucrose  and  saccharose  in  different  parts 
of  the  grape.     C.  E.  Acad.  Sci.  (1907),  vol.  24,  pp.  1376-79. 

Eoos,  L.,  and  Hughes,  E.,  The  sugar  of  the  grape  during  ripening.  Ann. 
Falsif.  (1910),  vol.  Ill,  p.  395. 

Bouffard,  A.,  Observations  in  regard  to  the  proportion  of  sugar  during  ripen- 
ing.    Ann.  Falsif.  (1910),  vol.  Ill,  pp.  394-5. 

Zeissig,  Investigations  on  the  process  of  ripening  on  one-year-old  grape  wood. 
Ber.  k.  Lehranst.  Wien,  Obst-u.  Garten-bau  (1902),  pp.  59-64. 

Koressi,  F.,  Biological  investigations  of  the  ripening  of  the  wood  of  the 
grape.  Eev.  Gen.  Bot.,  vol.  13  (1901),  no.  149,  pp.  193-211;  no.  150,  pp.  251-264; 
no.  151,  pp.  307-325. 

Brunet,  E.,  Analysis  and  composition  of  the  grape  during  ripening.  Eev. 
de  Viticulture,  vol.  37,  pp.  15-20. 

Garina,  C,  Variations  in  the  principal  acids  of  grape  juice  during  the  process 
of  maturing.  Canina.  Ann.  E.  acad.  d 'agricultura  di  Torino,  vol.  57  (1914), 
p.  233.  Cf.  Ann.  Chim.  applicata,  vol.  5  (1914),  pp.  65-6.  See  also  Ann.  r.  acad. 
d'agr.  di  Torino,  vol.  57,  pp.  233-90. 

Baragolia,  W.  I.,  and  Godet,  C,  Analytical  chemical  investigations  on  the 
ripening  of  grapes  and  the  formation  of  wine  from  them.  Landw.  Jahrb.,  vol. 
47  (1914),  pp.  249-302. 

Eiviere,  G.,  and  Bailhache,  G.,  Accumulation  of  sugar  and  decrease  of  acid 
in  grapes.  Chem.  Abs.  Jour.  (1912),  p.  1022;  Jour.  Soc.  Nat.  Hort.  France  (4), 
pp.  125-7;  Bot.  Cent.,  1912,  pp.  117,  431. 

Pantanelli,  Enzyme  in  must  of  overripe  grapes.  Chem.  Abs.  Jour.,  vol.  VI 
(1912),  p.  2447. 

*  Alwood,  W.  B.,  Hartmann,  J.  B.,  Eoff,  J.  E.,  and  Sherwood,  S.  F.,  Develop- 
ment of  sugar  and  acid  in  grapes  during  ripening.  U.  S.  Dept.  Agric.  Bull.  335, 
April  11,  1916. 

The  occurrence  of  sucrose  in  grapes.    Jour.  Indust.,  vol.  II,  Eng.  Chem. 

(1910),  pp.  481-82. 

Sugar  and  acid  content  of  American  native  grapes.     8th  Inter.  Cong. 

Appl.  Chem.  (1912),  Sect.  Vla-XIv,  pp.  33,  34. 

Enological  Studies:  the  chemical  composition  of  American  grapes  grown 

in  Ohio,  New  York,  and  Virginia.    U.  S.  Dept.  Agric.  Bur.  Chem.  Bull.  145,  1911. 

Crystallization  of  cream  of  tartar  in  the  fruit  of  grapes.     U.  S.  Dept. 

Agric.  Jour.  Agric.  Eesearch   (1914),  pp.  513,  514. 

Alwood,  W.  B.,  Hartmann,  B.  G.,  Eoff,  J.  E.,  Sherwood,  S.  F.,  Carrero,  J.  O., 
and  Harding,  T.  J.,  The  chemical  composition  of  American  grapes  grown  in  the 
central  and  eastern  states.    U  .  S.  Dept.  Agric. (  1916)  Bull.  452. 


1918]  Bioletti—Cruess-'Davi:  Chemical  Composition  of  Grapes  105 

investigations  referred  to,  there  is  a  slight  increase  in  both  of  these 
constituents. 

In  the  investigations  reported  in  the  present  paper,  particular 
attention  was  given  to  increase  in  total  solids  and  sugar,  decrease  in 
total  acid,  and  changes  in  protein  and  cream  of  tartar  in  the  must  or 
juice  of  the  grapes.  The  ripening  of  the  leaves  was  traced  by  noting 
the  changes  in  starch,  sugar,  acid,  and  protein  content. 

Sampling. — During  1914  and  1915  samples  of  fruit  were  taken 
from  the  time  the  grapes  had  reached  full  size  but  were  still  hard  and 
green  until  they  had  become  overripe.  During  1916  the  first  samples 
were  taken  shortly  after  the  berries  had  set  and  before  the  seeds  had 
formed.  The  last  samples  were  taken  when  the  grapes  had  become 
overripe.  Samples  of  leaves  were  also  taken  in  1916  on  the  same 
dates  that  samplings  of  the  grapes  were  made.  The  samples  were 
taken  at  intervals  of  approximately  one  week.  They  were  in  all  cases 
taken  from  the  experimental  vineyard  at  Davis.5 

Five-pound  samples  of  grapes  were  used.  The  grapes  were  picked 
from  the  first  crop,  except  in  1914,  when  a  comparison  of  the  ripening 
of  first  and  second  crops  was  made.  An  ordinary  five-pound  grape 
basket  was  filled  with  leaves  at  each  sampling.  The  samples  of  grapes 
and  leaves  were  shipped  from  the  vineyard  to  the  laboratory  at 
Berkeley,  where  the  grapes  were  placed  in  an  Enterprise  fruit  crusher 
and  pressed.  The  juice  was  sterilized  in  bottles  at  212°  F.  The  leaves 
were  ground  in  an  Enterprise  food  chopper  and  sterilized  at  212°  F 
in  wide  mouth,  air  tight  bottles.  The  samples  were  then  reserved  for 
chemical  examination. 

In  1914  it  was  found  that  there  was  considerable  irregularity  in 
the  variation  of  samples  from  week  to  week.  For  example,  instead 
of  an  increase  of  total  solids  during  the  periods  between  samplings,  a 
slight  decrease  was  found  in  a  few  samples.  During  the  1915  season 
it  was  therefore  considered  of  interest  to  note  what  effect  certain 
factors  might  have  upon  the  composition  of  samples  taken  on  the 
same  date. 

1.  Effect  of  Age  of  Vine.  The  entire  first  crop  from  three  large 
old  vines  and  from  three  small  young  vines,  all  of  the  Muscat  variety, 
was  picked,  crushed,  and  pressed.  Analyses  of  the  juices  were  made 
with  the  following  results : 


s  The  authors  wish  to  express  their  appreciation  of  the  assistance  of  F.  C. 
Flossfeder,  of  the  University  Farm  at  Davis,  who  gathered  most  of  the  samples 
reported  upon  in  this  paper. 


106  University  of  California  Publications  in  Agricultural  Sciences         [Vol.  3 

Table  1 — Effect  of  Age  of  Vine  on  Balling  and  Acid  of  Must  of  Muscat 

Grapes 

Vine  Balling  Acid 

Small,  no.  1  24.7  .67 

Small,  no.  2  27.7  .49 

Small,  no.  3  27.6  .67 

Large,  no.  1  22.0  .88 

Large,  no.  2  23.5  .75 

Large,  no.  3  23.6  .76 

Average,  small  26.7  .61 

Average,  large  23.0  .81 

Difference  3.7  —.20 

The  results  show  rather  strikingly  that  young  vines  ripen  their 
fruit  earlier  than  do  mature  vines.  This  fact  makes  it  essential  that 
samples,  to  be  comparative,  must  be  taken  from  vines  of  the  same  age. 

2.  Comparison  of  Grapes  from  North  and  South  Sides  of  Vines. 
The  whole  first  crop  from  three  large  Muscat  vines  was  picked.  The 
bunches  from  the  north  and  south  sides  of  each  vine  were  kept  sep- 
arate. They  were  crushed,  pressed,  and  analyzed  for  Balling  and  acid 
content. 

Table  2 — Comparison  of  Balling  and  Acid  of  Juice  From  Grapes  Picked  From 
North  and  South  Sides  of  Vines 

Vine  and  side  of  vine  Balling  Acid 

1-N  , 21.3  .92 

1-S   22.7  .84 

2-N  23.5  .81 

2-S   23.5  .80 

3-N  23.1  .81 

3-S   24.1  '      .71 

Average,  N  side  22.63  .85 

Average,  S  side  23.43  .78 

Difference   80  —.07 

The  tests  indicate  that  grapes  located  on  the  south  side  of  the  vine 
ripen  more  rapidly  than  those  on  the  north  side.  This  difference  is 
apparently  due  to  the  fact  that  the  south  side  of  the  vine  receives 
more  heat  than  the  north  side. 

3.  Effect  of  Location  of  Bunch  on  Cane.  Grapes  of  first  crop,  from 
canes  showing  two  bunches  each,  were  picked  and  the  bunches  from 
near  the  bases  of  the  canes  kept  separate  from  those  near  the  tip  of 
the  cane.  They  were  crushed,  pressed,  and  analyzed  for  Balling  and 
acid. 


1918]  Bioletti-Cruess-Davi :  Chemical  Composition  of  Grapes  107 

Table  3 — Effect  of  Location  of  Bunch  on  Cane 

Nearest  base  of  cane       Nearest  tip  of  cane 

A A 

Vine  Balling  Acid  Balling  Acid 

Muscat,  no.  1,  cane  1  25.1  .73  23.7  .83 

Muscat,  no.  1,  cane  2  25.6  .79  24.8  .80 

Muscat,  no.  2,  cane  1  25.1  .85  24.6  .87 

Muscat,  no.  2,  cane  2  25.2  .78  24.7  .85 

Muscat,  no.  3,  cane  1  23.0  .79  22.6  .82 

Muscat,  no.  3,  cane  2  24.5  .73  23.8  .73 

Muscat,  no.  4,  cane  1  24.2  .90  25.2  .90 

Muscat,  no.  4,  cane  2  24.5  .68  23.8  .83 

Tokay,  cane  1  21.2  .67  21.2  .80 

Tokay,  cane  2  23.0  .63  22.4  .76 

Sultanina,  cane  1  23.3  .61  22.3  .62 

Sultanina,  cane  2  22.5  .61  23.0  .63 

Sultana,  cane  1  23.2  .78  21.6  .70 

Sultana,  cane  2  21.1  .90  20.0  1.20 

Palomino,  cane  1  25.1  23.5  

Palomino,  cane  2  22.0  23.7 

Means   24.9  .75  23.1  .81 

The  data  indicate  that  bunches  at  the  base  of  the  cane  ripen  in  most 
cases  more  rapidly  than  those  near  the  tip,  although  this  relation  does 
not  always  hold  and  may  be  reversed  in  some  instances. 

4.  Variation  in  Balling  Degree  of  Must  from  Bunches  of  Similar 
Appearance  and  Size  from  Same  Vineyard  and  Gathered  on  Same 
Date.  A  five-pound  basket  of  grapes  of  first  crop  and  selected  for 
similarity  of  color,  size  of  bunch,  and  general  appearance  was  picked 
from  each  of  a  number  of  vines  in  the  same  vineyard.  Vines  of 
similar  size  and  appearance  were  chosen.  Several  varieties  were  rep- 
resented in  the  experiment.     Tests  of  Balling  degree  only  were  made. 

Table  4 — Variation  in  Balling  in  Must  From  Grapes  of  Same  Variety  Picked 
±,rom  Different  Vines  of  Similar  Appearance 


Variety 

Vine 
number 

Balling 

Mean 
Balling 

Maximum 
variation 

Cornichon 

3 

14.5 

Cornichon 

6 

15.0 

Cornichon 

9 

14.2 

Cornichon 

11 

14.7 

Cornichon 

16.1 

14.9 

1.9 

Emperor 

10 

12.0 

Emperor 

11 

14.5 

Emperor 

13 

15.2 

Emperor 

14 

15.5 

Emperor 

17 

15.0 

14.4 

3.5 

Malaga 

5 

18.5 

Malaga 

6 

17.2 

108 


University  of  California  Publications  in  Agricultural  Sciences        [Vol.  3 


Table  4 — {Continued) 


Variety 

Vine 
number 

Balling 

Mean 
Balling 

Maximum 
variation 

Malaga 
Malaga 
Malaga 
Muscat 

7 
9 

11 

* 

19.7 
18.5 
19.2 
21.7 

18.6 

2.0 

i,xuscat 

* 

21.1 

Muscat 

* 

20.9 

Muscat 

* 

21.5 

Muscat 

* 

21.7 

21.4 

.8 

Palomino 

3 

19.5 

Palomino 

4 

21.0 

Palomino 

6 

21.2 

Palomino 

7 

20.7 

Palomino 

9 

18.8 

20.2 

2.4 

Sultanina 

* 

22.5 

Sultanina 

* 

21.5 

Sultanina 

* 

18.7 

Sultanina 

* 

22.0 

Sultanina 

4r 

22.6 

21.5 

3.9 

Tokay 
Tokay 
Tokay 
Tokay 
Tokay 
Pedro  Zumbon 

■X- 
* 
* 

* 

7 

19.8 
19.3 
18.7 
20.7 
19.5 
21.5 

19.6 

2.0 

Pedro  Zumbon 

4 

21.2 

Pedro  Zumbon 

6 

20.6 

Pedro  Zumbon 

3 

18.5 

Pedro  Zumbon 

5 

19.8 

20.3 

3.0 

Emperor 
Emperor 
Emperor 

15 

8 
14 

18.1 
15.8 
16.2 

Emperor 
Emperor 
Cornichon 

9 

16 

4 

16.8 
16.3 
17.3 

16.6 

2.3 

Cornichon 

9 

16.3 

Cornichon 

10 

17.9 

Cornichon 

11 

17.8 

Cornichon 

13 

18.0 

17.5 

1.7 

Malaga 
Malaga 
Malaga 
Malaga 

4 
5 
6 

8 

18.3 
20.4 
20.0 
20.1 

19.7 

1.8 

Mean  variation,  six  ripest  varieties  2.32 

Mean  variation,  six  least  ripe  varieties 2.20 

Average  variation,  whole  series  2.30 


Adjacent  vines. 


1918]  Bioletti-Cruess-Davi:  Chemical  Composition  of  Grapes  109 

The  data  illustrate  the  difficulty  of  selecting  five-pound  lots  of  the 
same  variety  that  will  represent  average  samples. 

5.  Effect  of  Location  of  Berries  on  the  Bunch.  All  of  the  bunches 
of  the  first  crop  were  taken  from  two  Muscat  vines.  The  bunches 
were  cut  into  top  and  bottom  halves.  These  lots  were  crushed  sep- 
arately, pressed,  and  the  juices  analyzed. 

Table  5 — Effect  of  Location  of  Berries  on  Bunch 

Sample                                                                         Balling  Acid 

Vine  no.  1,  stem  end  of  bunch  23.6  .76 

Vine  no.   1,  apical  end  of  bunch  22.7  .87 

Vine  no.  2,  stem  end  of  bunch  21.3  .92 

Vine  no.  2,  apical  end  of  bunch  _ 21.3  .93 

The  results  show  that  considerable  variation  in  composition  of  the 
berries  may  exist  within  the  same  bunch. 

6.  Effect  of  Thoroughness  of  Pressing.  About  ten  pounds  of  Mus- 
cat grapes  were  crushed  and  lightly  pressed.  The  pulp  and  skins  left 
from  this  pressing  were  then  thoroughly  crushed  and  pressed  a  second 
time.    The  juices  from  the  two  lots  were  analyzed  separately. 

Table  6 — Effect  of  Thoroughness  of  Pressing 

Sample  Balling  Acid 

First  pressing  k.Z.8  .78 

Second  pressing  22.8  .79 

There  was  practically  no  difference  between  the  juices  from  lightly 
and  thoroughly  pressed  grapes  of  the  same  lot. 

The  data  from  the  above  six  tests  indicate  that  it  is  a  very  difficult 
matter  to  select  grapes  that  will  represent  a  fair  average  sample  of 
the  grapes  to  be  studied.  The  size  and  age  of  the  vine,  the  side  of 
the  vines,  the  location  of  the  bunch  on  the  cane,  and  individual  vines, 
all  affect  the  composition  of  the  juice  from  the  grapes  very  materially, 
and  these  factors  should  be  taken  into  account  when  samples  are 
taken. 

Preservation  of  Samples  and  Preparation  for  Analysis.— In  1914 
the  samples  of  juice  were  preserved  with  HgCl2,  1 :1000.  In  .1915  and 
1916  the  samples  were  sterilized  at  100°  C.  Before  analysis  the  bottles 
were  heated  to  100°  C  for  an  hour  to  dissolve  any  cream  of  tartar  which 
might  have  separated.  The  juices  were  filtered  before  analysis.  Con- 
siderable coagulation  of  dissolved  solids  took  place  during  sterilization. 


110  University  of  California  Publications  in  Agricultural  Sciences         [Vol.  3 

Methods  of  Analysis. — The  samples  were  analyzed  by  the  methods 
in  use  in  the  Agricultural  Chemistry  Laboratory  and  the  Nutrition 
Laboratory  of  this  station.    A  brief  description  of  the  methods  follows : 

1.  Total  Solids.  The  juice  was  filtered  clear  and  cooled  below 
15°  C.  The  specific  gravity  was  determined  by  a  pycnometer  at 
15? 5  C.  The  corresponding  total  solids,  or  extract,  was  found  from 
Windisch's  tables  in  Leach's  Food  Analysis,  page  697.  This  table 
gives  the  extract  as  "grams  per  100  grams";  that  is,  per  cent  by 
weight.  To  calculate  the  corresponding  grams  per  100  c.c,  the  per 
cent  by  weight  was  multiplied  by  the  specific  gravity.  This  gives  a 
figure  not  very  much  greater  than  grams  per  100  grams  in  juices  of 
low  specific  gravity,  but  gives  a  figure  as  much  as  2  per  cent  greater 
where  the  total  solids  are  much  above  20  per  cent.  The  two  methods 
of  reporting  total  solids  has  in  the  past  led  to  much  unnecessary 
confusion.  It  is  therefore  urged  that  the  reader  bear  in  mind  the 
distinction  between  the  two  methods  when  reading  the  discussions  in 
this  paper  or  examining  the  curves. 

2.  Sugar.  The  sample  was  filtered ;  an  aliquot  was  treated  with 
lead  acetate ;  diluted  to  mark ;  filtered ;  lead  removed  with  anhydrous 
Na2C03,  and  the  sugar  determined  in  an  aliquot  by  the  gravimetric 
method,  using  Soxhlet's  modification  of  Fehling's  solution.  The  Cu20 
was  weighed  directly  after  drying  at  100°  C.  The  corresponding 
sugar  as  invert  sugar  was  obtained  from  Munson  and  Walker's  table 
in  Leach's  Food  Analysis.  The  grams  of  invert  sugar  per  100  c.c. 
found  in  this  way  was  divided  by  the  specific  gravity  of  the  must  to 
obtain  the  corresponding  grams  per  100  grams  of  juice. 

3.  Total  acid  was  determined  by  titration  of  a  10  c.c.  sample  with 
N/10  NaOH,  using  phenolphthalein  as  an  indicator,  and  is  reported 
as  tartaric  acid,  grams  per  100  c.c. 

4.  Cream  of  tartar  was  estimated  by  a  method  suggested  by  Pro- 
fessor D.  R.  Hoagland  of  the  Division  of  Agricultural  Chemistry. 
Ten  c.c.  of  the  juice  was  incinerated  at  a  low  heat  in  a  muffle  furnace 
until  well  carbonized,  but  not  to  a  white  ash.  (Excessive  heating 
results  in  loss  of  K  by  volatilization.)  The  K2CO:;  formed  by  incin- 
eration was  leached  out  with  hot  water  and  a  known  excess  of  N/10 
HC1  added.  This  was  titrated  back  with  N/10  NaOH,  using  methyl 
orange  as  an  indicator.  The  K2C03  is  obtained  by  difference  and 
calculated  back  to  cream  of  tartar,  assuming  that  all  of  the  K2C03  is 
formed  by  the  oxidation  of  cream  of  tartar,   KH(C4H406).     It  is 


1918]  Bioletti-Cruess-Davi:  Chemical  Composition  of  Grapes  111 

reported  as  grams  KH(C4H4O0)    per  100  c.c.,  and  also  as  tartaric 
acid. 

5.  Free  Tartaric  Acid  was  obtained  by  difference  between  total  acid 
and  cream  of  tartar  calculated  as  tartaric  acid.  It  is  reported  as 
grams  per  100  c.c. 

6.  Protein  in  the  juice  was  determined  by  the  usual  Kjeldahl- 
Gunning  method  upon  a  10  c.c.  sample.  It  is  reported  as  grams  per 
100  c.c. 

7.  Moisture  in  the  leaves  was  determined  by  drying  the  sample  at 
100°  C. 

8.  Sug;ar  in  the  leaves  was  estimated  by  leaching  the  dried  sample 
with  cold  water  and  determining  sugar  by  the  gravimetric  Fehling 
method  in  the  filtrate. 

9.  Starch  in  the  leaves  was  determined  by  hydrolysis  of  the  dried 
ground  sample  with  dilute  HC1  at  100°  C,  followed  by  filtration  and 
the  usual  gravimetric  Fehling  method  for  juice  described  above. 

10.  Protein  in  the  leaves  was  determined  by  the  Kjeldahl-Gunning 
method  on  .5  gram  samples. 

11.  Acid  in  the  leaves  was  estimated  by  leaching  in  hot  water  and 
titrating  in  the  presence  of  the  leaves,  using  litmus  paper  as  indicator. 

Analyses  of  Musts  from  Grape-Ripening  Samples,  1914, 1915,  1916. 
The  data  from  the  analyses  have  been  assembled  in  the  following 
tables.  Owing  to  the  size  of  the  tables,  abbreviations  have  been 
necessary  for  the  headings  of  the  columns. 

Explanations  op  Headings  of  Tables 

1.  Sp.  gr.  ==  Specific  gravity  at  15?  5  C. 

2.  T.  S.  G.  =  Total  solids  in  grams  per  100  grams. 

3.  T.'  S.  C.  =  Total  solids  in  grams  per  100  c.c. 

4.  S.  G.  7=  Sugar  in  grams  per  100  c.c. 

5.  S.  I.  =  Sugar  in  grams  per  100  grams. 

6.  Tl.  A.  =  Total  acid  in  grams  per  100  c.c. 

7.  C.  T.  =  Cream  of  tartar  in  grams  per  100  c.c. 

8.  C.  T.  T.  =  Cream  of  tartar  as  tartaric  acid,  grams  per  100  c.c. 

9.  T.  A.  =  Total  free  acid  as  tartaric  obtained  by  subtracting  cream  of  tartar 
as  tartaric  from  total  acid  as  tartaric. 

10.  P.  =  Protein,  grams  per  100  c.c. 

11.  S.  =  Sum  of  sugar,  cream  of  tartar,  tartaric  acid,  and  protein  in  grams 
per  100  c.c. 

12.  T.  S.  — S.  =  Total  solids  (T.  S.  C.)  — S  (preceding  column). 


112 


University  of  California  Publications  in  Agricultural  Sciences        [Vol.  3 


Table  7 — Grape  Eipening  Tests,  1914 
(Grapes  from  Davis) 


Malaga 

First  crop: 

Variety 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

n 

12 

and  date 

Sj>.  gr. 

T.  S.  G. 

T.  S.  C. 

S.  G. 

S.I. 

Tl.  A. 

0.  T. 

C.T.  T, 

.  T.  A. 

p. 

S. 

T.  S.  S. 

Aug.  19 

1.0396 

10.25 

10.65 

7.32 

7.04 

2.78 

.35 

.13 

2.65 

.21 

10.53 

.12 

Aug  26 

1.0413 

10.69 

11.13 

7.84 

7.53 

2.65 

.36 

.14 

2.51 

.25 

10.96 

.17 

Aug.  26 

1.0595 

15.42 

16.33 

13.37 

12.62 

.77 

.48 

.19 

.58 

.55 

14.98 

1.41 

Aug.  26 

1.0613 

15.87 

16.84 

14.31 

13.50 

1.46 

.31 

.12 

1.34 

.33 

16.29 

.55 

Aug.  26 

1.0694 

18.01 

19.25 

16.59 

15.52 

1.00 

.36 

.14 

.86 

.38 

18.19 

1.06 

Aug.  31 

1.0732 

19.00 

20.39 

17.65 

16.45 

.87 

.55 

.22 

.65 

.45 

19.30 

1.09 

Sept.  23 

1.0736 

19.10 

20.50 

17.83 

16.60 

.74 

.38 

.15 

.59 

.52 

19.32 

1.18 

Oct.   5 

1.0965 

25.12 

27.54 

24.89 

22.70 

.72 

.50 

.20 

.52 

.57 

26.48 

1.06 

Second  crop: 

Aug.  10 

1.0213 

5.51 

5.62 

2.07 

2.03 

3.22 

.23 

.09 

3.13 

.17 

5.60 

.02 

Aug.  31 

1.0495 

12.82 

13.45 

9.58 

9.13 

2.51 

.40 

.16 

2.35 

.28 

12.61 

.84 

Sept.  14 

1.0532 

13.78 

14.51 

11.89 

11.30 

2.07 

.37 

.15 

1.92 

.31 

14.49 

.02 

Sept.  23 

1.0670 

17.43 

18.60 

15.29 

14.33 

1.54 

.50 

.20 

1.35 

.29 

17.43 

1.17 

Sept.  23 

1.0869 

22.59 

24.55 

22.04 

20.19 

1.07 

.45 

.18 

.89 

.41 

23.79 

.76 

Oct.   5 

1.0930^ 

24.20 

26.45 

23.90 

21.87 

.94 

.48 

.19 

.75 

.41 

25.54 

.91 

Tokay 

First  crop: 

Aug.  2 

1.0454 

11.75 

12.28 

'  8.73 

8.35 

2.63 

.46 

.18 

2.45 

.32 

11.96 

.32 

Aug.  10 

1.0624 

16.08 

17.08 

14.28 

13.44 

1.56 

,.45 

.18 

1.38 

.27 

16.38 

.70 

Aug.  19 

1.0682 

17.69 

18.90 

15.94 

14.92 

1.32 

.45 

.18 

1.14 

.27 

17.80 

1.10 

Aug.  3i 

1.0849 

22.09 

23.97 

21.87 

20.16 

.63 

.59 

.23 

.40 

.40 

23.26 

.71 

Sept.  4 

1.0865 

22.49 

24.44 

22.21 

20.44 

.77 

.43 

.17 

.60 

.32 

23.56 

.88 

Sept.  4 

1.0912 

23.72 

25.88 

23.44 

21.48 

.59 

.64 

.25 

.44 

.41 

24.93 

.95 

Sept.  23 

1.0937 

24.38 

26.66 

24.15 

22.08 

.58 

.49 

.19 

.30 

.39 

25.33 

1.33 

Oct.  14 

1.0991 

25.80 

28.36 

25.55 

23.25 

.45 

.54 

.21 

.24 

.45 

26.78 

1.58 

Oct.  14 

1.1000 

26.04 

28.64 

25.78 

23.44 

.52 

.58 

.23 

.29 

.58 

27.23 

1.41 

Second  crop: 

Aug.  19 

1.0657 

17.04 

18.16 

15.03 

14.10 

1.91 

.50 

.20 

1.70 

.32 

16.55 

.61 

Sept.  14 

1.0701 

18.19 

19.47 

16.68 

15.59 

1.29 

.52 

.21 

1.11 

.33 

18.64 

.83 

Sept.  23 

1.0769 

19.95 

21.48 

19.22 

17.85 

1.01 

.48 

.19 

.82 

.40 

20.92 

.56 

Oct.  14 

1.0911 

23.70 

25.86 

23.43 

21.47 

.69 

.60 

.24 

.45 

.40 

24.88 

.98 

Table  8 — Grape  Eipening  Tests,  1915 
(Grapes  from  Davis) 


Uomichon 

Variety 
and  date 

l 

Sp.  gr. 

2  . 
T.  S.  G. 

3 
T.  S.  C. 

4 
S.  G. 

5 

S.  I. 

6 
Tl.  A. 

C.  T. 

8 
C.T.  T. 

9 
T.  A. 

10 

p. 

11 

S.  ■ 

12 
T.  S.  S. 

Aug.  22 

1.0324 

8.38 

8.65 

3.99 

3.86 

3.05 

.58 

.23 

2.82 

.38 

7.77 

.88 

Sept.  1 

1.0514 

13.31 

13.99 

10.70 

10.18 

1.62 

.61 

.25 

1.37 

.42 

13.10 

.89 

Sept.  15 

1.0688 

17.85 

19.08 

15.94 

14.91 

.97 

.70 

.28 

.69 

.43 

17.76 

1.32 

Sept.  22 

1.0723 

18.76 

20.12 

16.97 

15.83 

.94 

.71 

.28 

.66 

.46 

18.80 

1.32 

Sept.  29 

1.0737 

19.13 

20.54 

18.31 

17.05 

.87 

.75 

.30 

.61 

.66 

20.33 

.21 

Oct.   7 

1.0781 

20.28 

21.86 

19.41 

18.02 

.71 

.73 

.29 

.42 

.48 

21.04 

.82 

Oct.  14 

1.0843 

21.91 

23.76 

20.40 

18.81 

.78 

.68 

.27 

.62 

.66 

22.36 

1.40 

Oct.  22 

1.0873 

22.70 

24.68 

21.06 

19.37 

.75 

.78 

.31 

.44 

.46 

22.74 

1.94 

1938] 


Bioletti-Crucss-Davi :  Chemical  Composition  of  Grapes 


113 


Emperor 


Table  8 — {Continued) 


Variety 
and  date 

l 

Sp.  gr. 

2 

T.  S.  G. 

3 

T.  S.  C. 

4 

S.  G. 

5 
S.I. 

6 
Tl.  A. 

7 
0.  T. 

8 
C.  T.  T. 

9 
T.  A. 

10 

p. 

ll 

S.   1 

12 

\  A.  S 

Aug.  19 

1.0420 

10.87 

11.33 

6.96 

6.68 

2.33 

.38 

.15 

2.18 

.38 

9.90 

1.43 

Sept.  1 

1.0479 

12.40 

12.99 

9.82 

9.37 

1.89 

.40 

.16 

1.73 

.62 

12.57 

.42 

Sept.  7 

1.0560 

14.51 

15.32 

11.48 

10.87 

1.70 

.47 

.19 

1.57 

.54 

14.00 

1.32 

Sept.  15 

1.0632 

16.37 

17.40 

14.88 

14.00 

1.40 

.53 

.21 

1.18 

.54 

17.13 

.27 

Sept  22 

1.0652 

16.91 

18.01 

15.46 

14.51 

.93 

.48 

.19 

.74 

.55 

17.23 

.78 

Sept.  29 

1.0672 

17.43 

18.60 

16.37 

15.34 

.91 

.48 

.19 

.72 

.66 

18.23 

.37 

Oct.   7 

1.0744 

19.31 

20.75 

17.82 

16.59 

.79 

.58 

.23 

.56 

.51 

19.47 

1.28 

Oct.  14 

1.0765 

19.86 

21.38 

18.37 

17.06 

.79 

.59 

.24 

.56 

.63 

20.15 

1.23 

Oct.  22 

1.0792 

20.57 

22.20 

19.81 

18.36 

.75 

.63 

.25 

.49 

.66 

21.59 

.61 

Malaga 

Aug.  19 

1.0546 

14.14 

14.91 

12.47 

11.82 

2.05 

.36 

.15 

1.90 

.75 

15.48 

.57 

Aug.  2o 

1.0651 

16.86 

17.96 

.14.53 

13.64 

1.66 

.46 

.18 

1.48 

.90 

17.37 

.59 

Sept.  1 

1.0678 

17.59 

18.78 

16.75 

15.69 

1.38 

.44 

.18 

1.20 

.89 

19.28 

.50 

Sept.  7 

1.0719 

18.66 

19.50 

17.00 

15.86 

1.29 

.44 

.18 

1.11 

.70 

19.25 

.25 

Sept.  15 

1.0758 

19.68 

21.17 

18.17 

16.89 

1.21 

.62 

.25 

.96 

.70 

20.45 

.72 

Sept.  22 

1.0760^ 

19.81 

21.32 

18.39 

17.09 

1.18 

.61 

.25 

.93 

.74 

20.67 

.65 

Sept.  29 

1.0812 

21.20 

22.92 

18.48 

17.09 

1.07 

.58 

.23 

.84 

.75 

20.65 

2.27 

Oct.   7 

1.0838 

21.78 

23.61 

21.03 

19.40 

1.07 

.65 

.26 

.81 

.73 

23.22 

.39 

Oct.  14 

1.0970 

25.25 

27.70 

24.58 

22.41 

.59 

.83 

.33 

.26 

.88 

26.55 

1.15 

Muscat 

Aug.  19     1.0615     15.94  16.92  13.93  13.12     1 

Aug.  25     1.0744     19.31  20.75  17.96  16.72     1.2 

Sept.    1     1.0805     20.91  22.59  19.50  18.05 

Sept.    7     1.0827     21.47  23.25  20.39  18.83 
23.85 


Sept.  15  1.0917 


26.04  23.49  21.52 


Sept.  22  1.0954  24.14  26.44  24.54  22.40 
Sept.  29  1.1048  27.30  30.16  27.01  24.45 
Oct.   7  1.1079  28.12  31.15  28.28  25.53 


70 

.36 

.15 

1.55 

.70 

16.54 

.38 

21 

.62 

.25 

.96 

.62 

20.16 

.59 

79 

.63 

.25 

.54 

.63 

21.30 

1.29 

76 

.65 

.26 

.50 

.66 

22.20 

1.05 

96 

.58 

.23 

.73 

.58 

25.38 

.66 

77 

.62 

.25 

.52 

.85 

26.53 

.09 

72 

.72 

.29 

.44 

.72 

28.89 

1.27 

66 

.59 

.23 

.43 

.66 

29.96 

1.19 

eclro  Zum 

bon 

Aug.  19 

1.0555 

14.38 

15.18 

11.96 

11.33 

1.81 

.68 

.27 

1.54 

.33 

14.51 

.67 

Aug.  25 

1.0588 

15.24 

16.14 

13.77 

13.01 

1.09 

.57 

.23 

.86 

.53 

15.73 

.41 

Sept.  1 

1.0642 

16.64 

17.71 

15.61 

14.67 

.58 

.52 

.21 

.37 

.43 

16.93 

.78 

Sept.  7 

1.0693 

17.98 

19.23 

16.55 

15.48 

.84 

.48 

.19 

.65 

.73 

18.41 

.82 

Sept.  15 

1.0708 

18.37 

19.67 

18.17 

16.97 

.56 

.58 

.23 

.33 

.64 

19.72 

.05 

Sept,  22 

1.0912 

23.72 

25.88 

23.02 

21.10 

.53 

.87 

.35 

.19 

.64 

24.72 

1.16 

Sultana 


Aug.  19 

1.0673 

17.80 

19.00 

15.63 

16.64 

1.69 

.33 

.13 

1.56 

.32 

17.84 

1.16 

Aug.  25 

1.0746 

19.37 

20.82 

17.96 

16.71 

1.44 

.37 

.14 

1.30 

.38 

20.01 

.81 

Sept,  1 

1.0815 

21.17 

22.90 

20.26 

18.73 

1.14 

.54 

.22 

.92 

.50 

22.22 

.68 

Sept.  7 

1.0893 

23.22 

25.29 

23.02 

21.13 

.78 

.44 

.18 

.60 

.34 

24.40 

.89 

Sept.  22 

1.0902 

23.39 

25.50 

23.10 

21.19 

1.24 

.50 

.20 

1.04 

.38 

25.02 

.48 

Sept.  29 

1.0922 

23.99 

26.20 

24.04 

22.01 

.80 

.41 

.17 

.63 

.42 

25.50 

.70 

114 


University  of  California  Publications  in  Agricultural  Sciences        [Vol.  3 


Table  8 — (Continued) 


Sultanina 

Variety 
and  date 

1 
Sp.  gr. 

2 
T.  S.  G. 

3 
T.  S.  C. 

4 
S.  G. 

5 
S.  I. 

6 
Tl.  A. 

7 
C.  T.  ( 

8 
3.T.T 

9 
T.  A. 

10 

p. 

11     12 

S.   T.  A.  S. 

Aug.  19 

1.0673 

17.46 

18.64 

15.87 

14.87 

1.27 

.44 

.18 

1.09 

.42 

17.82 

.82 

Aug.  25 

1.0743 

19.26 

20.69 

18.30 

17.03 

1.19 

.47 

.19 

1.00 

.37 

20.14 

.55 

Sept.  1 

1.0771 

20.02 

21.56 

18.98 

17.62 

.85 

.49 

.20 

.65 

.42 

20.54 

1.02 

Sept.  7 

1.0892 

23.20 

25.27 

22.42 

20.58 

.72 

.80 

.32 

.40 

.62 

24.24 

1.03 

Sept.  15 

1.0927 

24.12 

26.36 

23.62 

21.62 

.79 

.76 

.30 

.39 

.45 

25.22 

1.14 

Sept.  22 

1.0984 

25.62 

28.14 

25.71 

23.41 

.60 

.58 

.23 

.37 

.45 

27.11 

1.03 

Sept.  29 

1.1049 

27.33 

30.20 

27.41 

24.81 

.54 

.51 

.20 

.34 

.42 

28.68 

1.52 

Tokay 

Aug.  19 

1.0598 

15.50 

16.43 

14.41 

13,60 

1.74 

.41 

.16 

1.58 

.29 

16.69 

.26 

Aug.  25 

1.0676 

17.54 

18.73 

15.63 

14.64 

1.24 

.39 

.15 

1.09 

.69 

17.80 

.93 

Sept.  1 

1.0757 

19.65 

21.14 

18.17 

16.89 

.84 

.47 

.19 

.66 

.44 

19.74 

1.40 

Sept.  7 

1.0781 

20.28 

21.86 

19.11 

17.73 

.79 

.45 

.18 

.61 

.37 

20.54 

1.32 

Sept,  15 

1.0785 

20.39 

21.99 

19.26 

17.86 

.74 

.48 

.19 

.55 

.40 

20.69 

1.30 

Sept.  22 

1.0798 

20.73 

22.38 

20.17 

18.68 

.59 

.51 

.20 

.39 

.36 

21.43 

.95 

Sept,  29 

1.0823 

21.38 

23.14 

20.76 

19.18 

.85 

.58 

.23 

.62 

.28 

22.24 

.90 

Oct.   7 

1.0830 

21.57 

23.36 

20.87 

19.27 

.69 

.63 

.25 

.44 

.42 

22.36 

1.00 

Oct.  14 

1.0851 

22.12 

24.00 

21.53 

19.84 

.65 

.69 

.28 

.38 

.36 

22.96 

1.04 

Oct.  22 

1.0895 

23.28 

25.36 

22.91 

21.03 

.66 

.72 

.29 

.37 

.37 

24.37 

.99 

Table  9 

— Grape  Eipening  Tests, 

1916 

Burger 

Variety 
and  date 

l 
Sp.  gr. 

2 
T.  S.  G. 

3 
T.  S.  C. 

4 

S.  G. 

5 
S.I. 

6 
Tl.  A. 

7 

C.  X. 

8 
3.T.T 

9 
T.  A. 

10 

p. 

n 

S. 

12 

T.  S.  S. 

June  12 

1.0212 

5.48 

5.59 

1.29 

1.55 

2.95 

.55 

.22 

2.73 

.44 

5.27 

.32 

June  19 

1.0195 

5.04 

5.88 

.87 

.88 

2.88 

.51 

.21 

2.67 

.45 

4.51 

1.37 

June  27 

1.0220 

5.69 

5.82 

1.25 

1.28 

2.94 

.33 

.13 

2.81 

.45 

4.87 

.95 

July  7 

1.0220 

5.69 

5.82 

1.11 

1.28 

2.98 

.49 

.20 

2.78 

.31 

4.86 

.96 

July  10 

1.0200 

5.17 

5.27 

.93 

.95 

3.32 

.57 

.23 

3.09 

.37 

4.97 

.30 

July  19 

1.0205 

5.30 

5.41 

1.03 

1.05 

3.13 

.55 

.22 

2.91 

.35 

4.86 

.55 

July  27 

1.0225 

5.82 

5.95 

1.13 

1.15 

2.93 

.48 

.19 

2.74 

.34 

4.71 

1.24 

Aug.  3 

1.0258 

6.67 

6.84 

2.14 

2.19 

2.71 

.63 

.25 

2.46 

.40 

5.68 

1.16 

Aug.  7 

1.0330 

8.53 

8.83 

3.36 

3.46 

2.67 

.87 

.35 

2.32 

.47 

7.12 

1.21 

Aug.  16 

1.0391 

10.11 

10.51 

5.90 

6.13 

2.41 

.95 

.38 

2.03 

.46 

9.57 

.94 

Aug.  23 

1.0422 

10.92 

11.38 

6.03 

6.27 

2.10 

.98 

.39 

1.71 

.63 

9.59 

1.89 

Aug.  30 

1.0529 

13.70 

14.42 

9.95 

10.42 

1.15 

1.03 

.41 

.74 

.49 

12.70 

1.72 

Sept.  5 

1.0645 

16.73 

17.81 

14.51 

15.43 

1.01 

1.07 

.43 

.68 

.61 

17.79 

.02 

Sept.  12 

1.0717 

18.61 

19.94 

16.27 

17.36 

.95 

.98 

.39 

.56 

.82 

19.72 

.22 

Sept.  20 

1.0765 

19.86 

21.37 

17.44 

18.73 

.87 

1.06 

.42 

.45 

.62 

20.86 

.51 

Sept.  26 

1.0808 

20.99 

22.68 

18.48 

19.99 

.81 

1.01 

.40 

.41 

.83 

22.24 

.44 

Cornichon 

June  12 

1.0202 

5.22 

5.32 

.91 

.93 

3.15 

.64 

.26 

2.89 

.32 

4.78 

.54 

June  19 

1.0200 

5.17 

5.27 

.86 

.88 

2.96 

.62 

.25 

2.71 

.42 

4.63 

.64 

June  27 

1.0193 

4.99 

5.08 

.84 

.86 

2.89 

.39 

.16 

2.73 

.56 

4.54 

.44 

July  7 

1.0201 

5.19 

5.29 

.87 

.89 

2.88 

.44 

.18 

2.70 

.52 

4.55 

.74 

July  10 

1.0206 

5.32 

5.43 

.85 

.87 

3.27 

.54 

.22 

3.05 

.53 

4.99 

.44 

July  19 

1.0225 

5.82 

5.95 

1.28 

1.30 

3.11 

.57 

.23 

2.88 

.55 

5.30 

.65 

July  27 

1.0242 

6.25 

6.40 

1.63 

1.66 

2.94 

.54 

.22 

2.72 

.44 

5.26 

.14 

Aug.  3 

1.0373 

9.65 

10.00 

5.00 

5.19 

2.87 

.59 

.24 

2.63 

.56 

8.97 

1.03 

1918] 


Bioletti-Cruess-Davi :  Chemical  Composition  of  Grapes 


115 


Table 

9— (Co 

ntinue 

*) 

Variety 
and  date 

1 
Sp.  gr. 

2 
T.  S.  G. 

3 
T.  S.  C. 

4 

S.  G. 

S.I. 

6 
Tl.  A. 

7      8 
C.  T.  C.T.T 

9 
T.  A. 

10 

P. 

11     12 
S.   T.  A.  S 

Aug.   7 

1.0375 

9.70 

10.06 

5.28 

5.48 

2.79 

.65 

.26 

2.53 

.66 

9.32 

.64 

Aug.  16 

1.0434 

11.23 

11.71 

6.30 

6.57 

2.75 

1.06 

.43 

2.32 

.53 

10.48 

1.23 

Aug.  23 

1.0635 

16.47 

17.51 

12.19 

12.96 

1.85 

1.06 

.43 

1.42 

.58 

16.02 

1.49 

Aug.  30 

1.0685 

17.77 

18.97 

14.75 

15.61 

1.16 

1.10 

.44 

.72 

.63 

18.06 

.91 

Sept.  5 

1.0694 

18.01 

19.25 

15.03 

16.07 

.93 

.90 

.36 

.57 

.58 

18.12 

1.13 

Sept.  12 

1.0757 

19.65 

21.09 

16.37 

17.60 

.87 

1.14 

.46 

.41 

.78 

19.97 

1.12 

Sept.  20 

1.0786 

20.41 

22.00 

17.52 

18.88 

.84 

.94 

.37 

.44 

.59 

20.85 

1.15 

Sept.  26 

1.0828 

21.52 

23.30 

18.52 

20.03 

.72 

.83 

.33 

.39 

.85 

22.10 

1.20 

uscat 
June  12 

1.0203 

5.25 

5.35 

.91 

.93 

2.93 

.65 

.26 

2.71 

.38 

4.67 

.68 

June  19 

1.0199 

5.14 

5.24 

.70 

.72 

3.37 

.63 

.25 

3.12 

.44 

4.91 

.33 

June  27 

1.0210 

5.43 

5.54 

1.33 

1.36 

3.33 

.48 

.19 

3.14 

.49 

5.47 

.07 

July  7 

1.0210 

5.43 

5.54 

1.63 

1.66 

3.32 

.54 

.22 

3.10 

.45 

5.75 

.21 

July  10 

1.0195 

5.04 

5.14 

1.33 

1.36 

3.60 

.55 

.22 

3.38 

.36 

5.65 

.51 

July  19 

1.0251 

6.49 

6.65 

2.55 

2.61 

3.40 

.58 

.2~3 

3.17 

.49 

6.85 

.20 

July  27 

1.0308 

7.97 

8.22 

3.56 

3.67 

2.67 

.66 

.26 

2.01 

.45 

6.79 

1.43 

Aug.  3 

1.0488 

12.64 

13.26 

9.72 

10.19 

1.77 

.68 

.27 

1.50 

.46 

12.83 

.43 

Aug.  7 

1.0582 

15.68 

16.58 

12.72 

13.53 

1.60 

.73 

.29 

1.31 

.55 

16.12 

.46 

Aug.  16 

1.0803 

20.86 

22.53 

16.81 

18.15 

1.16 

.94 

.38 

.78 

.51 

20.38 

1.70 

Aug.  23 

1.0910 

23.67 

25.82 

20.20 

22.04 

.82 

1.04 

.42 

.40 

.56 

24.04 

1.78 

Aug.  30 

1.0972 

25.30 

27.75 

21.87 

22.99 

.65 

1.21 

.49 

.16 

.58 

25.94 

1.81 

Sept.  5 

1.1023 

26.64 

29.36 

23.28 

24.74 

.60 

1.17 

.47 

.13 

.65 

26.69 

2.67 

Sept.  12 

1.1101 

28.70 

31.85 

25.95 

27.83 

.56 

1.35 

.54 

.02 

.69 

29.89 

1.96 

Sept.  20 

1.1122 

29.25 

32.72 

26.43 

29.39 

.68 

1.56 

.63 

.05 

.58 

31.27 

1.45 

Sept.  26 

1.1133 

29.54 

32.89 

26.68 

29.70 

.56 

1.39 

.56 

.00 

.59 

31.57 

1.32 

Table  10 — Catawba  Grape  Eipening  Tests 


(Table  from  U.  S.  Dept.  Agric. 

Bulletin  335,  by 

*W.  B 

Alwood) 

Catawba 

1912: 

Variety 
and  date 

l 

Sp.  gr. 

2 
T.  S.  G. 

3 
T.  S.  C. 

4 

S.  I. 

5 

S.  G. 

6 
Tl.  A. 

7 
C.  T. 

8     9 
C.  T.  T.  Days 

Sept.  4 

1.0329 

8.51 

8.84 

3.60 

3.72 

3.68 

.39 

.16 

0 

Sept.  9 

1.0419 

10.84 

11.29 

6.68 

6.96 

3.02 

.41 

.16 

5 

Sept.  12 

1.0515 

13.34 

14.03 

9.35 

9.78 

2.48 

.46 

.18 

8 

Sept.  17 

1.0537 

13.91 

14.66 

10.38 

10.95 

2.12 

.45 

.18 

13 

Sept.  24 

1.0569 

14.74 

15.58 

11.33 

11.96 

1.74 

.53 

.21 

20 

Oct.   1 

1.0614 

15.92 

16.89 

12.75 

13.48 

1.63 

.54 

.22 

27 

Oct.   7 

1.0663 

17.20 

18.34 

13.79 

14.71 

1.53 

.61 

.24 

33 

Oct.  16 

1.0725 

18.82 

20.18 

15.35 

16.46 

1.34 

.61 

.24 

42 

Oct.  23 

1.0716 

18.58 

19.90 

15.01 

16.09 

1.28 

.59 

.24 

47 

Oct.  29 

1.0769 

19.97 

21.50 

16.49 

17.75 

1.22 

.57 

.23 

53 

Nov.  4 

1.0790 

20.52 

22.14 

16.77 

18.08 

1.28 

.71 

.28 

59 

Nov.  8 

1.0755 

19.60 

21.07 

16.39 

17.61 

1.09 

.52 

.21 

63 

116  University  of  California  Publications  in  Agricultural  Sciences         [Vol.  3 

Curves  of  Total  Solids,  Sugar,  Total  Acid,  Free  Acid,  and  Cream 
of  Tartar. — In  order  to  present  the  data  in  a  form  in  which  they  may 
be  readily  studied,  graphs  have  been  constructed  using  time  in  days 
as  abscissae  and  the  above  constituents  expressed  in  grams  per  100  c.c. 
as  ordinates.  The  curves  represent  the  data  for  1914,  1915,  and  1916. 
For  comparison,  curves  of  the  changes  in  composition  of  Catawba 
grapes  reported  by  W.  B.  Alwood  in  the  United  States  Department 
of  Agriculture  Bulletin  335  have  been  included.  The  acid  principles 
have  been  plotted  to  a  scale  five  times  as  great  as  that  used  for  total 
solids  and  sugar  in  order  that  the  variations  in  acidity  might  be  more 
apparent. 

Discussion  of  Graphs  of  Total  Solids,  Sugar,  Total  Acid,  Cream  of 
Tartar,  and  Free  Acid. —  (1)  Total  Solids  and  Sugar.  The  data  are 
more  complete  for  1916  than  for  1914  or  1915,  and  include  the  period 
during  which  the  berries  are  growing  to  full  size  as  well  as  the  ripen- 
ing period  itself,  during  which  the  rapid  increase  in  sugar  occurs. 
The  curves  for  1916,  therefore,  are  of  more  interest  than  those  for 
1914  and  1915.  In  the  case  of  the  Burger  variety,  total  solids  and 
sugar  remained  constant  for  approximately  forty  days  after  the  tests 
were  started.  There  was  then  a  slight  rise  in  these  components  for 
a  period  of  about  ten  days.  From  that  point  on  the  rise  in  total  solids 
and  sugar  was  very  rapid  and  fairly  uniform.  The  behavior  of  the 
Cornichon  was  very  similar. 

The  Muscat  began  ripening  about  ten  days  earlier  than  the  Burger 
and  Cornichon,  and  proceeded  much  more  rapidly  up  to  about  the 
ninetieth  day  after  the  experiment  was  started.  There  was  then  a 
slowing  up  in  the  increase  in  total  solids  and  sugar  corresponding  to 
the  period  of  over-ripeness.  This  slower  increase  in  total  solids  is 
also  evident  in  the  curves  for  Emperor,  Muscat,  Sultana,  and  Tokay 
for  the  1915  season,  and  would  undoubtedly  show  in  all  cases  if  the 
observations  were  continued  sufficiently. 

The  effect  of  the  season  upon  the  rate  of  ripening  is  shown  by  a 
comparison  of  the  Cornichon  and  Muscat  varieties  for  1915  and  1916. 
All  varieties  ripened  more  slowly  in  1915  than  in  1916,  resulting  in 
steeper  curves  for  1916.  However,  owing  to  the  fact  that  sampling 
was  started  later  in  1914  and  1915  than  in  1916,  the  curves  for  the 
former  two  years  show  only  the  changes  taking  place  during  the  latter 
half  of  the  ripening  period.  No  very  close  comparisons  therefore  can 
be  made  of  the  three  years. 

The  Catawba  reported  by  Alwood,  and  for  which  curves  appear 


1918] 


Biolc.tti-Cruess-Davi :  Chemical  Composition  of  Grapes 


11.7 


30 


MMJjGA  A W  CffOR  SQ/4 


&=  7afa/  flaW, 


f?cc  Torfarjc 


irrd  Cham  r>  t 


7arrtG 


WL <J?/?72 


/=kr  /OOcc 


i)'    7n/bf  C)f)/irJ&    mo/  \5//pa 


7/713 


Fhr  /OOcs 


Fig.  1 — Malaga  first  and  second  crops,  1914. 


118  University  of  California  Publications  in  Agricultural  Sciences         [Vol.  3 


"3 TO 75 TZZ ^3 S3 33 =92? "=h 3E 33= Z5 

T/ME  /N  OfrVS 

Fig.  2 — Tokay  first  and  second  crops,  1914. 


1918] 


Bioletti-Cruess-Davi:  Chemical  Composition  of  Grapes 


119 


7Z 73 -&1 3$ 

77  ML  //V   DfhyS 


Fig.  3 — Cornichon  and  Emperor,  1915. 


120 


University  of  California  Publications  in  Agricultural  Sciences         [Vol.  3 


TIME  IN  DftVD 


Fig.  4 — Malaga  and  Muscat,  1915. 


1918] 


Bioletti-Crucss-Davi :  Chemical  Composition  of  Grapes 


121 


m 


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Total  ffcidifar.Jirhfic  andGmninf^'t^hLGai^^Ecj^-lQIkL^ 


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T/M£T  IN  OrJ-ys 


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Fig.  5 — Pedro  Zumbon  and  Sultana,  1915. 


122 


University  of  California  Publications  in  Agricultural  Sciences        [Vol.  3 


(c  wd '  Own?  o/\  lartcr  Gnri  Pet 


2^=  /o?tL  So, 


'ids  avaESLLLiar  &r?o  Z5E  f(Xt 


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1Z 75 -&? 30        66 

TIME  IN  DfF/S 

Fig.  6 — Sultanina  and  Tokay,  1915. 


—u 


1918] 


Biolctti-Cruess-Davi:  Chemical  Composition  of  Grapes 


\2?j 


—70 3D ^D 3S— 

TIME  IN  PHY  5 


Fig.  7 — Burger  and  Cornichon,  1916. 


124 


University  of  California  Publications  in  Agricultural  Sciences        [Vol.  3 


-JO ~&> 3£ =9& 3& ^0 7& ZD Pa~ 

nME:  in  D/rys 

Fig.  8— Muscat,  1916. 


Fig-.  9— Catawba  (U.  S.  Dept.  Agric.  Bull.  335). 


1918]  Bioletti-Cruess-Davi :  Chemical  Composition  of  Grapes  125 

in  figure  9,  ripened  more  slowly  than  the  Vinifera  varieties.  For 
example,  during  a  period  of  fifty  days,  the  total  solids  increased  only 
4  per  cent.  It  can  not  be  said  from  the  data  at  hand  whether  this 
slow  ripening  is  due  to  the  conditions  under  which  the  grapes  were 
grown  or  to  the  variety. 

By  reference  to  figures  1  and  2  it  may  be  seen  that  the  general 
form  of  the  ripening  curves  is  the  same  for  the  first  and  for  second 
crop.  In  one  case,  the  Malaga,  the  curves  are  almost  identical  for 
the  period  common  to  both,  i.e.,  from  10.6  Bal.  to  26.3  Bal.,  showing 
an  equal  rate  of  ripening.  In  the  other,  the  Tokay,  the  curve  of  the 
second  crop,  from  18.2  Bal.  to  24.6  Bal.,  is  much  flatter  than  that  of 
the  first,  indicating  a  rate  of  ripening  with  the  latter  of  about  two 
and  a  half  times  that  of  the  former.  This  difference  can  be  accounted 
for  by  the  cooler  weather  during  the  time  the  second  crop  Tokay  was 
ripening,  which  was  about  ten  days  later  than  in  the  case  of  the  second 
crop  Malaga.  The  slower  ripening  is  probably  due  both  to  the  direct 
effect  of  the  cool  weather  and  to  the  decreased  activity  of  the  leaves 
at  lower  temperatures. 

(2)  Changes  in  Total  Acid,  Cream  of  Tartar,  and  Free  Acid. 
Owing  to  the  fact  that  the  analyses  were  started  in  1914  and  1915 
after  ripening  had  commenced,  the  curves  for  these  years  show  a 
decrease  in  acid  throughout  the  period  of  the  tests.  In  1916,  however, 
a  rise  in  total  acid  occurred  during  the  growing  stage,  as  shown  by 
a  rise  in  the  curve  during  the  first  thirty  days  of  the  experiment. 
Although  this  rise  is  not  very  large,  it  is  quite  definite,  and  occurs 
in  all  three  varieties  tested.  The  rise  was  most  positive  in  the  case 
of  the  Muscat  grape,  and  amounted  to  .67  per  cent  acid  as  tartaric. 
From  the  point  of  maximum  acidity,  the  total  decreases  slowly  until  the 
period  of  rapid  ripening  sets  in.  The  total  acid  then  decreases  very 
rapidly  for  a  time  and  more  or  less  in  proportion  to  the  increase  in 
total  solids  and  sugar.  As  the  grapes  near  maturity,  the  rate  of  de- 
crease of  total  acid  becomes  less  and  the  total  remains  practically 
constant  after  the  grapes  have  reached  maturity. 

The  cream  of  tartar  in  general  increases  very  slightly  during  the 
periods  of  growth  and  ripening. 

The  increase  in  total  acid  during  the  first  stages  of  growth  is  due 
to  increase  in  the  free  acid.  Since  the  cream  of  tartar  remains  almost 
constant  throughout  the  ripening  period,  the  curve  of  the  free  acid 
is  practically  parallel  with  that  of  the  total  acid. 

As  the  grapes  approach  maturity,  the  cream  of  tartar  calculated  as 


126 


University  of  California  Publications  in  Agricultural  Sciences         [Vol.  3 


tartaric  acid  approaches  the  total  acid,  and  in  one  case,  (Musct,  1916), 
actually  became  equal  to  the  total  acid,  indicating  that  in  this  instance 
no  free  acid  remained. 

Second  crop  grapes  were  found  to  be  higher  in  free  acid  than 
first  crop  grapes  of  the  same  total  solids  and  sugar  content.  The 
Catawba  grape  grown  under  eastern  conditions  (fig.  9)  exhibits  rela- 
tively high  free  acid.  Alwood6  has  found  this  free  acidity  in  eastern 
grapes  to  be  due  largely  to  malic  acid.  No  attempt  was  made  in  the 
analyses  of  the  California  samples  to  identify  the  various  acids  making 
up  the  free  acidity  which  was  calculated  as  tartaric  acid. 

Mean  Differences  Between  Total  Solids  and  Sugar. — The  following- 
table  contains  figures  representing  the  differences  between  total  solids 
and  sugar  at  the  various  percentages  of  total  solids  indicated  at  the 
tops  of  the  columns.  The  data  represent  a  range  of  total  solids  from 
5  per  cent  to  30  per  cent.  The  figures  were  taken  from  the  data 
reported  in  tables  7  to  9,  and  represent  several  varieties  of  grapes. 
Only  a  few  determinations  of  total  solids  and  sugar  were  available 
for  the  lower  concentrations  (5  per  cent  to  15  per  cent),  and  therefore 
the  figures  for  this  range  may  not  represent  averages  so  accurately 
as  the  figures  above  15  per  cent  total  solids. 

Between  5  per  cent  and  11  per  cent  solids,  the  average  difference 
between  total  solids  and  sugar  remains  practically  constant.  From 
11  per  cent  to  17  per  cent  total  solids,  the  mean  difference  decreases 
quite  rapidly.  From  17  per  cent  to  30  per  cent,  the  difference  remains 
fairly  constant.     The  variations  noted  after  17  per  cent  total  solids 


Fig.  10 — Mean  differences  between  total  solids  and  sugar  between  5  per  cent 
and  30  per  cent  total  solids. 


U.  S.  Dept.  Agric.  Bull.  335. 


1918]  Bioletti-Cnicss-Vavi :  Chemical  Composition  of  Crapes  127 


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128 


University  of  California  Publications  in  Agricultural  Sciences        [Vol.  3 


was  reached  are  probably  within  the  experimental  error.  The  large 
difference  between  the  total  solids  and  sugar  noted  4uring  the  first 
stages  of  ripening  is  no  doubt  due  to  the  high  acid  content  of  the 
unripe  grapes.  The  fact  that  the  difference  remains  fairly  constant 
after  the  grapes  have  become  mature  is  to  be  expected,  because  the 
cream  of  tartar,  total  acid,  and  protein  remain  fairly  constant  as 
maturity  is  approached  and  during  the  periods  of  maturity  and  over- 
ripeness. 


TU 7D ZTC7 VD 7ZJS 77V 

Fig.  11 — Variation  in  non-coagulable  protein  content  for  three  varieties,  1916. 


Protein. — The  total  nitrogen  content  of  the  various  samples  was 
multiplied  by  6.25  to  convert  it  into  its  protein  equivalent.  Owing 
to  the  fact  that  the  samples  were  sterilized  by  heat  and  filtered  before 
analysis,  the  figures  represent  only  the  protein  not  coagulated  by  heat. 

The  curves  show  that  there  is  a  slow  increase  in  protein  content 
during  growth  and  ripening  and  the  greatest  increase  occurs  during 
the  period  of  most  rapid  increase  of  sugar  and  most  rapid  decrease 
of  acid.  The  increase  amounted  to  about  .2  per  cent  in  the  case  of  the 
Muscat  and  .6  per  cent  in  the  case  of  the  Cornichon.  The  increase 
seems  to  be  quite  definite,  although  the  protein  curves  are  not  so 
regular  as  those  of  total  solids,  sugar,  and  total  acid. 


1918]  Bioletti-Cruess-Davi :  Chemical  Composition  of  Grapes  129 


Summary  of  Changes  in  Must  of  Grapes  During  Growth  and 
Ripening  of  Berries 

1.  Total  Solids. — The  total  solids  remain  fairly  constant  during 
the  period  of  growth,  corresponding  to  the  period  between  setting  of 
the  berries  and  the  time  at  which  the  berries  have  reached  almost 
full  size  but  are  still  hard  and  green.  From  this  point  on,  there  is  a 
rapid  increase  in  total  solids  due  to  increase  in  sugar. 

After  the  period  usually  considered  as  full  maturity  is  reached, 
the  increase  in  total  solids  is  slow.  The  question  may  be  raised  as  to 
whether  this  last  increase  is  due  to  an  actual  synthesis  and  secretion 
of  sugar  or  other  solids,  or  simply  to  evaporation  of  water.  The  fact 
that  there  is  no  change  in  the  curve  of  the  acid  decrease  at  this  time 
indicates  that  the  same  processes  are  continuing  and  that  the  increased 
Balling  degree  represents  an  actual  increase  of  solids.  This  view  is 
fortified  by  observations  regarding  the  increase  of  weight  of  solids 
during  the  ripening  of  raisin  grapes.  It  has  been  shown  that  the 
weight  of  dried  grapes  shows  a  continuous  increase  up  to  the  highest 
degree  observed,  28.75  Balling.7 

2.  Sugar. — The  total  sugar  during  the  growth  period  comprises 
only  a  small  amount  of  the  total  solids.  During  ripening,  the  sugar 
rapidly  increases  and  then  constitutes  a  much  greater  proportion. 
During  ripening,  the  sugar  curve  follows  the  total  solids  curve  closely. 
It  is  more  or  less  the  mirror  image  of  the  total  acid  curve  multiplied 
by  five,  i.e.,  increases  as  the  acid  decreases. 

3.  Total  Acid  and  Free  Acid. — During  the  early  stages  of  the 
growth  of  the  berries,  the  acidity  increases  owing  to  an  increase  of 
free  acid.  This  is  a  fact  that  the  authors  have  not  found  mentioned 
in  the  literature.  During  ripening,  the  total  and  free  acid  rapidly 
decrease.    After  maturity  is  reached,  the  decrease  is  very  slow. 

4.  Cream  of  Tartar. — There  is  a  very  slow,  but  usually  fairly  defi- 
nite, increase  in  cream  of  tartar  during  ripening.  This  increase  is 
very  much  less  than  the  decrease  in  free  acid,  and  therefore  can  not 
account  for  any  great  part  of  this  decrease. 


7  Bioletti,  Frederic  T.,  Eelation  of  the  maturity  of  the  grapes  to  the  quantity  and 
quality  of  the  raisins.  Proc.  Inter.  Cong,  of  Viticulture,  San  Francisco,  1915, 
pp.  307-314. 


130  University  of  California  Publications  in  Agricultural  Sciences         [Vol.  3 

5.  Protein. — The  protein  not  coagulated  by  heat  increased  defi- 
nitely during  growth  and  ripening,  although  the  increase  was  not  so 
regular  nor  so  marked  as  the  increase  in  sugar  or  the  decrease  in  total 
acid. 

6.  Difference  Between  Total  Solids  and  Sugar. — This  factor  re- 
mained constant  for  the  lower  percentages  of  total  solids,  decreased 
during  the  rapid  ripening  stage,  and  remained  constant  through 
maturity  and  over-ripeness. 


